Concrete forms



P. A. SEABURG A CONGRETE FORMS Filed Aug. 2, 1968 Feb. 24, 1970lA/VEA/TORS Pau/ Jeabury o) fl/berf J Ol/dhcusden Jr:

United States Patent 3,496,691 CONCRETE FORMS Paul A. Seaburg, Mequon,Wis., and Albert J. Oudheusden, Jr., Bethlehem, Pa., assignors toBethlehem Steel Corporation, a corporation of Delaware Filed Aug. 2,1968, Ser. No. 749,640 Int. Cl. E04b 1/16, 5/18 US. Cl. 52336 4 ClaimsABSTRACT OF THE DISCLOSURE A sheet metal concrete form intended for usein floor and roof construction. The form serves initially as a supportfor wet concrete and temporary construction loads, and finally as themain positive reinforcement for the concrete slab when the concrete hasset and cured. The form has a plurality of alternating dovetail groovesand triangular closed ribs. The ribs are perforated so that concrete isable to enter and fill the interior of the ribs and lock the concreteslab to the sheet metal form and create an integral composite slab.

BACKGROUND OF THE INVENTION This invention relates to concrete forms andmore particularly to forms made of sheet metal which are leftpermanently in place after the pouring of concrete for roof and floorslabs in buildings.

Roofs and floors for commercial and industrial buildings are oftenconstructed by placing a series of wooden or sheet metal forms on thetops of supporting joists and girders, spacing steel reinforcing bars ormesh above the forms and then depositing a layer of fresh concrete onthe forms and around the reinforcement to the desired slab thickness.With this type of construction the form serves only as a support for thefresh concrete and, in many cases, is stripped or removed once theconcrete has set and cured. Contractors usually find the removal of theforms from the underside of the slabs, not only difficult but also timeconsuming and expensive. For this reason many contractors prefer to useforms which can be left permanently in place.

Heretofore in situations where the forms have been permanently left inplace, the forms contributed very little to the strength or loadcarrying capacity of the finished slab. The strength of the slab wasobtained primarily from the concrete and conventional reinforcing barsor mesh embedded in the concrete. It generally was not possible to getsufficient bond between the concrete and the top surface of the formwhich would permit the form and slab to act as a composite unit andthereby permit the loads imposed on the finished floor to be carried tothe supporting girders and joists.

In addition, since many of the slabs serve as ceilings for the floorbelow, it was usually necessary to install false ceiling to hide therather unattractive undersides of the forms.

Many of the heretofore known forms also were expensive, diflicult toinstall and unsuited to serve as a support for piping, ducts, electricalconduits, false ceilings and the like which are used regularly in modernbuilding construction.

SUMMARY OF THE INVENTION It is therefore an object of this invention toprovide a permanent metal form for concrete floor slabs or the likewhich also Serves as the main positive reinforcement for the finishedconcrete slab.

It is a further object of this invention to provide a permanent metalform for concrete floor slabs or the like 3,496,691 Patented Feb. 24,1970 which will coact compositely with the concrete in the slab whensubject to loads.

It is a still further object of this invention to provide a permanentmetal form for concrete floor slabs or the like which is easy toinstall, presents a smooth, attractive appearance on the underside andcan serve as a support for suspended ceilings, pipes, ducts and thelike.

Other and further objects of this invention will become apparent fromthe following description and the accompanying drawing and claims.

It has been discovered that the foregoing objects can be attained by asheet metal form having a plurality of spaced parallel perforatedsubstantially triangular closed ribs formed on the top surface thereof.

BRIEF DESCRIPTION OF DRAWINGS The figure is a perspective view,partially in section, of a concrete slab constructed according to thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the figure, theform 1 is fabricated from a rectangular metal sheet and is designed torest upon and extend between joists or girders 2 spaced at suitableintervals. The forms 1 are preferably made of galvanized steel for highstrength and long life.

As shown in the figure, the forms 1 have a continuous, substantiallyflat bottom surface 3 and a top surface comprising a plurality ofdovetail troughs 4 separated by a plurality of parallel, substantiallytriangular ribs 5. The sidewalls 6 of each rib 5 abut one another at thebase of the rib 5 thereby forming a closed hollow cell 7 within the rib5.

The sidewalls 6 of each rib 5 are provided with a series of relativelylarge diameter apertures 8 which connect the hollow interior of the cell7 with the dovetail troughs 4. The apertures 8 are staggered so that anaperture 8 in one sidewall 6 of a rib 5 is located approximately midwaybetween two adjacent apertures 8 in the other sidewall 6 of the same rib5.

The side edges of the form 1 are designed to permit interlocking ofadjacent sheets. One edge is bent to form a short, upturned curvedflange 9 while the opposite side edge is bent to form a short,downturned curved flange 10 as a short projection of the outer sidewall6 of the last rib 5.

As illustrated in the figure, adjacent forms 1 are placed with the ribs5 extending perpendicular to the joists or girders 2, and are snappedtogether into locking engagement by placing the outermost rib 5 of oneform 1 over the upturned flange 9 at the side edges of the adjacentsheet. Pressing or stepping on the rib 5 will drive the flange 9 inbetween the converging sidewalls 6 of the rib which in turn will pressagainst the upturned flange 9 causing it to fit tightly against theshort downturned flange 10 of the overlapping form 1.

Since the bottom surface 3 of the form 1 is flat and continuous and theribs 5 are closed at the bottom, there is no need to provide endclosures or to tightly abut the ends of adjacent sheets together toprevent concrete leakage as is usually the case with conventionalcorrugated forms.

When the forms 1 are in place, they are secured to the tops of thegirders or joists 2 by welding, self-tapping screws, clips or the like.In the embodiment shown in FIGURE 1, shear connectors 14 in the shape ofshort channels are welded to the tops of forms 1 and girders 2 toprovide composite action in a direction parallel to the girders. Any ofthe other well known types of shear connectors could be used in place ofthe channels 14, if desired.

If rewired, electrical ducts or conduits (not shown) can be placed inthe trough 4 or across the tops of the ribs 5 before placing theconcrete 11 on top of the forms 1.

After all the forms 1 are properly positioned and secured to the girdersand joists 2, a layer of fresh concrete 11 is poured on top of the forms1 to the desired depth. The concrete 11 not only fills the dovetailtroughs 4 but also covers the ribs 5 and enters into the hollow interiorof the ribs 5 through apertures 8 and substantially fills the hollowcells 7 as shown in the figure.

If desired, lightweight welded steel wire fabric 12 may be placedslightly below the upper surface 13 of the concrete slab 11 to reducecracking due to shrinkage and temperature changes.

During the pouring of the concrete 11, the form 1 serves as a supportfor the wet concrete and the workmen. However, once the concrete 11 hasset and cured, the metal form 1 serves as the main positivereinforcement for the concrete slab. The unique combination of thedovetail troughs 4 and the apertures 8 in the sidewalls 6 of the ribs 5provide a strong mechanical bond that tightly locks the concrete slab 11to the steel reinforcing form 1.

As a result of the excellent concrete to steel bond, and the resultingcomposite action, one is able to eliminate the need for conventionalreinforcing bars or mesh in the slab with the result that constructioncosts can be greatly reduced.

A preferred embodiment of this invention is a form approximately 18inches wide having three 2 inch high ribs spaced 6 inches apart. Theapertures punched in the sidewalls of the ribs are inch diameter holesspaced 3 inches apart. The lengths of the form range from about 6 to 15feet. The forms are constructed of galvanized steel in thicknessesbetween 18 and 26 gauge.

What is claimed is:

1. A concrete slab construction, in combination, a plurality ofoverlapping rectangular metal backing sheets,

said sheets having a plurality of spaced parallel perforated hollowclosed ribs projecting from one surface thereof and a layer of concreteon said sheets covering said ribs and substantially filling the hollowinterior of said ribs.

2. A backing for receiving, supporting, strengthening and interlockingwith cementitious material comprising a rectangular metal sheet having aplurality of spaced parallel perforated hollow closed ribs projectingfrom one surface thereof.

3. A form for receiving, supporting, strengthening and interlocking withcementitious material comprising a rectangular metal sheet having acontinuous, substantially flat bottom surface and a top surfacecomprising a plurality of dovetailed troughs separated by parallelsubstantially triangular ribs, the two sidewalls of each rib meeting atthe base of said rib forming a closed hollow cell, said sidewalls beingprovided with a series of apertures extending between the hollowinterior of said cell and the dovetailed troughs.

4. The form of claim 3 in which the perforations in one of saidsidewalls are offset from the perforations in the other sidewall.

References Cited UNITED STATES PATENTS 764,989 7/1904 Chester 52450FOREIGN PATENTS 278,186 10/1927 Great Britain.

HENRY C. SUTHERLAND, Primary Examiner J. L. RIDGILL, JR., AssistantExaminer US. Cl. X.R.

